Objective: To investigate the targeted regulation of miR-204 on mitochondrial transcription factor A (TFAM) in breast cancer cells and their relations with cell growth and proliferation. Methods: Human breast cancer MDA-MB-231 cells were transfected with miR-204 mimics or inhibitors, and then, the miR-204 and TFAM protein expressions were determined by real-time PCR and Western blot, respectively. The luciferase reporter plasmids (mut-TFAM/wt-TFAM) were constructed and co-transfected with miR-204 mimics or inhibitors into MDA-MB-231 cells, and then, changes in luciferase activities were detected. The pcDNA3.1/TFAM plasmids were constructed and transfected alone or co-transfected with miR-204 mimics into MDA-MB-231 cells, and then, the TFAM protein expressions were measured, and cell growth and proliferation were analyzed by TTC and BrdU assay. Results: The miR-204 mRNA expression was significantly increased, and TFAM protein expression was significantly decreased in MDA-MB-231 cells after transfection with miR-204 mimics, while, opposite directional changes were found after transfection with miR-204 inhibitors (all P<0.05). The luciferase activity was significantly decreased after transfection with miR-204 mimics, but was significantly increased after transfection with miR-204 inhibitors (both P<0.05). In MDA-MB-231 cells, both expressions of TFAM mRNA and protein were significantly up-regulated, and the growth and proliferation were significantly enhanced after transfection of pcDNA3.1/TFAM (all P<0.05), and the growth and proliferation were significantly impaired along with significant down-regulation of TFAM protein expression after transfection of miR-204 mimics, which were all partially abolished by co-transfection with pcDNA3.1/TFAM (all P<0.05). Conclusion: MiR-204 exerts targeted inhibition on TFAM expression in breast cancer cells, and thereby suppresses the growth and proliferation of breast cancer cells.